Transmission housing with integral pump assembly

ABSTRACT

A transmission has an integral lubrication system for delivering lubricating fluid to transmission components. The central portion of the lubrication system is conveniently located within the intermediate wall of the housing. The housing has an opening and inlet and outlet ports in fluid communication with the opening. A pumping assembly having inner and outer rotors is disposed within the opening for moving the fluid from the inlet port to the outlet port. A pump cover is attached to the intermediate wall over the opening and the rotors. An inlet and outlet chamber is defined within the opening by the pump cover and space between the inner and outer rotors. The inlet and outlet chambers are in fluid communication with the inlet and outlet ports, respectively, so the pump may draw the fluid from the inlet port into the inlet chamber and then expel the fluid into the outlet chamber and to the outlet port. The intermediate wall also contains integrally formed inlet and main feed passageways. The inlet passageway interconnects the inlet chamber and a sump that stores the fluid and provides fluid communication between them. The main feed passageway interconnects the outlet chamber and a distribution system that delivers the fluid to a plurality of transmission components within the housing.

RELATED APPLICATION

This disclosure is filed with Applicants'copending application havingthe Ser. No. 09/344,171 filed concurrently herewith and entitled“Transmission Housing with Integral Lubrication System.” Eachapplication is directed to different inventions.

BACKGROUND OF THE INVENTION

This invention relates to a transmission housing, or more specifically,to a transmission housing having an intermediate wall with an integralpump assembly.

Transmissions have lubrication systems that circulate lubricating fluidwithin the transmission housing to various transmission components toreduce the friction of those components and lower the temperature of thetransmission. The lubrication system may be discussed in terms of threemain portions: the collection system, the distribution system, and thepump which draws fluid from the collection system and moves it throughthe distribution system.

Typically, these three portions utilize many separate components whichadds cost to the transmission. For example, prior art lubricationsystems utilize pump assemblies that have a separate housing which areattached as a separate unit to a portion of the housing, such as theintermediate wall between a main and auxiliary portion of the housing.The pumps have an inlet chamber that is in fluid communication with thesump via oil collection passages and an outlet chamber in fluidcommunication with the distribution system via oil distributionpassages. Often these passages are formed by tubes that are supported bythe housing externally of the intermediate wall. Therefore, what isneeded is a pump assembly and oil passages that are integral with thetransmission housing so that the pump housing and other components maybe eliminated while still achieving a robust lubrication system design.

SUMMARY OF THE INVENTION AND ADVANTAGES

The present invention provides a transmission having an integrallubrication system for delivering lubricating fluid to transmissioncomponents. The central portion of the lubrication system isconveniently located within the intermediate wall of the housing. Thehousing has an opening and inlet and outlet ports in fluid communicationwith the opening. A pumping assembly having inlet and outlet rotors isdisposed within the opening for moving the fluid from the inlet port tothe outlet port. A pump cover is attached to the intermediate wall overthe opening and the rotors. An inlet and outlet chamber is definedwithin the opening by the pump cover and space between the inner andouter rotors. The inlet and outlet chambers are in fluid communicationwith the inlet and outlet ports, respectively, so the pump may draw thefluid from the inlet port into the inlet chamber and then expel thefluid into the outlet chamber and to the outlet port.

The intermediate wall also contains integrally formed inlet and mainfeed passageways. The inlet passageway interconnects the inlet chamberand a sump, which stores the fluid, and provides fluid communicationbetween them. The main feed passageway interconnects the outlet chamberand a distribution system that delivers the fluid to a plurality oftransmission components within the housing.

Accordingly, the above described invention provides a lubrication systemthat eliminates many of the components of the prior art by integrallyforming lubrication system components within the intermediate wall.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention can be understood by referenceto the following detailed description when considered in connection withthe accompanying drawings wherein:

FIG. 1 is a schematic view of a cross-section of a manual transmissionfor a heavy vehicle;

FIG. 2 is a cross-sectional view taken along line 2—2 in FIG. 1 showingthe intermediate wall of the present invention;

FIG. 3 is a partial cross-sectional view taken along line 3—3 in FIG. 2;

FIG. 4A is a partial cross-sectional view taken along line 4A—4A in FIG.2 showing the pump assembly of the present invention;

FIG. 4B is a partial cross-sectional view taken along line 4B—4B in FIG.3A showing the pump assembly of the present invention;

FIG. 5 is a partial cross-sectional view taken along line 5—5 in FIG. 2showing the pump assembly of the present invention;

FIG. 6 is a partial cross-sectional view taken along line 6—6 in FIG. 1;

FIG. 7 is a partial cross-sectional view taken along line 7—7 in FIG. 6;

FIG. 8 is a cross-sectional view taken along line 8—8 in FIG. 1;

FIG. 9 is a cross-sectional view taken along line 9—9 in FIG. 1;

FIG. 10 is a cross-sectional view taken along line 10—10 in FIG. 9; and

FIG. 11 is a schematic of the lubrication fluid flow path of the presentinvention lubrication system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a transmission 10 for a heavy vehicle has a housing12. The housing 12 has three sections: a main box 14, an auxiliary box16, and a clutch housing 18. A plurality of shafts 22,24,25,26,27,28having a plurality of gears 30 are supported within the main 14 andauxiliary 16 boxes. More specifically, the main box 14 has maincountershafts 22, an input shaft 24 and a main shaft 25. It also hasreverse idler shafts 27 that support reverse idler gears 31. Theauxiliary box 16 has auxiliary countershafts 26 and an output shaft 28.While the auxiliary box is shown with only two gear sets, the auxiliarysection could also be a combined range and splitter box. An intermediatewall 33 separates the main 14 and auxiliary 16 boxes and supportsportions 17 of the shafts 22,25,26,27.

Together, the shafts 22,25,26,27,28 and gears 30,31 cooperate tomultiply speed from the engine 34 to achieve a desire gear ratio. Theclutch housing 18 has a clutch 36 interconnecting the input shaft 24 andthe engine 34 to selectively couple and decouple the engine 34 andtransmission 10 together.

Because the shafts 22,25,26,27,28 and gears 30,31 rotate under load,they generate friction and heat. As a result, transmissions incorporatelubrication systems for delivering lubricating fluid, or oil, to varioustransmission components to reduce friction and dissipate the heat.Referring now to FIG. 2, the intermediate wall 33 has a portion of alubrication system 40 of the present invention integrally formed betweenopposing surfaces. The lubrication system 40 has a collection system 42and a distribution system 44 to circulate the oil throughout thetransmission 10. The collection system 42 collects the oil after it hasbeen used to lubricate and cool the transmission components. Thedistribution system 44 carries the oil from the collection system 42back to the transmission components. A pump assembly 50 (shown in FIG.4A) draws the oil from the collection system 42 from an inlet port 46and expels it out an outlet port 48 to move the oil through thedistribution system 44.

With continuing reference to FIG. 2, the collection system 42 has a sump52 defined by a lower portion 54 of the housing 12 which collects theoil that drains back from the transmission components. An inletpassageway 56 is integrally and internally formed within theintermediate wall 33 and interconnects the sump 52 and the inlet port 46to provide fluid communication between them. That is, when the termintegrally or internally is used it is meant that the passageway has acomponent that is generally parallel to the opposing surfaces of aportion of the housing. Said another way, the passageway is not simply ahole extending through the housing from one surface to the opposingsurface. The inlet passageway 56 includes a plurality of branches 58that are connected to different portions of the sump 52 so that oil fromdifferent areas of the transmission may be drawn into the inletpassageway 56 to be distributed by the pump assembly 50.

As mentioned above, the shafts 22,25,26,27 have bearing portions 17supported by the housing 12. Intermediate wall 33 has bores 60 thatsupport the bearing portions 17 so that the shafts 22,25,26,27 mayrotate within the bores 60. The collection system 42 further includes areturn passageway 62, at least a portion of which is integrally formedwithin the intermediate wall 33. The return passageway 62 has aconnecting tube 64 that intersects the bore 60 and a hole 66 thatextends through the intermediate wall 33.

The distribution system 44 has a plurality of fluid distribution portsfor delivering the fluid to a plurality of transmission components, suchas the bearing portion 17. For convenience sake, the distribution system44 may be discussed in terms of segments, or passageways and is in noway intended to limit the scope of the invention. The distributionsystem 44 has a main feed passageway 68, or first passageway, integrallyformed within the intermediate wall 33. The main feed passageway 68interconnects the outlet port 48 and the rest of the distribution system44 to provide fluid communication between the pump assembly 50 and thetransmission components that require oil.

The distribution system 44 has a second passageway 72, a portion ofwhich runs generally parallel with the shafts 22,24,25,26,27,28 in anupper portion 70 of the housing 12. The second passageway 72 carries theoil from the first passageway 68 in the intermediate wall 33 to othercomponents throughout the transmission 10. A third passageway 74interconnects the second passageway 72 and the bores 60. A distributionport 76 is formed where the third passageway 74 intersects the bores 60for delivering the oil to the bearing portions 17.

The inlet 56, first 68, second 72, and third 74 passageways arecontiguous and integrally formed within portions of the housing 12during a lost foam casting process. As part of this process, a foampattern is made which corresponds to the desired shape of the housing12. The pattern is placed in a mold and completely covered with sand oranother suitable material so that the sand penetrates all the cavitieswithin the pattern. Thus, during the casting process the passageways68,72,74 are filled with sand. Molten aluminum is then poured into themold thereby evaporating the foam pattern. The resulting aluminumhousing is removed from the mold and all the sand shaken out.

Although the passageways 56,68,72,74 of the collection 42 anddistribution 44 systems are shown integrally formed, it is to beunderstood that not all portions need be integrally formed within thehousing 12. That is, an ordinary worker will appreciate that onlyportions of the collection 42 and distribution 44 systems may beintegrally formed to come within the scope of the present invention.Said another way, tubes or some other external fluid carrying device maybe used in conjunction with the integrally formed passageways to carrythe oil to a portion of the transmission. Moreover, any combination ofintegrally formed passageways may be used while others may not be used.Further, the passageways are not limited to being located within theintermediate wall 33, but may be located anywhere within the housing 12,such as the auxiliary box 16 or clutch housing 18.

The distribution system 44 includes several pressure control deviceswhich regulate the oil pressure within the system. One such device is asolenoid 80 located within a boss 82 on the housing 12. The solenoid 80is used to slow the rotating transmission components by increasing theload placed on them, as disclosed in Ser. No. 08/931,379 now U.S. Pat.No. 5,988,344 entitled “Fluid Power Transmission Clutch Brake.” This isaccomplished by increasing the load on the pump assembly 50, which iscoupled to the main shaft 24 through the reverse idler gear 31 (shown inFIG. 4A).

The solenoid 80 is disposed within the first passageway 68 between theoutlet port 48 and the distribution ports that carry the oil to thetransmission components, such as distribution port 76. The solenoid 80has a normally open and closed position in which the first passageway 68is unobstructed and blocked by the solenoid 80, respectively. When thesolenoid is in the normally open position, the oil exits the controlboss through control boss passageway 83 and continues to flow along thesecond passageway 72.

A clutch signal 84 is connected to the solenoid 80 for preparing thetransmission to change between gears 30,31. The clutch signal 84actuates the solenoid 80 to the closed position which blocks the firstpassageway 68 and increases the pressure on the pump assembly 50 and theload on the gears 30,31. In this manner, the rotating transmissioncomponents are slowed in preparation for a gear shift.

A first pressure relief bore 88 is connected to the first passageway 68so that they are in fluid communication with one another. The firstpressure relief bore 88 is positioned between the solenoid 80 and theoutlet port 48. The first pressure relief bore 88 has a first ventingorifice 90 that is in fluid communication with the sump 52. A firstpressure relief valve 92, which may be a ball check valve, is disposedwithin the first pressure relief bore 88. The first pressure reliefvalve 92 has a normally closed position and an open position in whichthe first venting orifice 90 is blocked and unobstructed, respectively.The first pressure relief valve 92 works in conjunction with thesolenoid 80 so that if an undesirably high pressure is reached the firstpressure relief valves 92 moves to the open position thereby permittingthe oil to escape through the first venting orifice 90 and back to thesump 52.

An oil cooler 96 may be added to the lubrication system 40 to reduce theoil temperature, and thus, the temperature of the transmissioncomponents. The oil cooler 96 may be located along the first passageway68 between the solenoid 80 and the distribution ports and connected by asupply 95 and return 97 line.

When a solenoid is used, the second relief is necessary to protect thecooler and distribution system. A second pressure relief valve 98, orcheck ball valve, may be connected to the first passageway 68 in theboss 82, best shown in FIG. 3.

Referring to FIG. 3, a second pressure relief bore 100 is positionedbetween the solenoid 80 and the oil cooler 96. The second pressurerelief bore 100 has a second venting orifice 102 in fluid communicationwith the sump 52. The second pressure relief valve 98 has a normallyclosed position and an open position in which the second venting orifice102 is blocked and unobstructed, respectively. The second pressurerelief valve 98 moves to the open position when the oil reaches apredetermined pressure to protect the distribution system 44. With thesecond pressure relief valve 98 open, the oil is permitted to escapethrough the second venting orifice 102 and back to the sump 52. Thesecond pressure relief valve 98 is set to vent at a lower pressure thanthe first pressure relief valve 92.

It is to be understood that relief valves, solenoid, and oil cooler maybe arranged differently than described above, or any one of them may beomitted from a particular lubrication distribution system. For example,the oil cooler may be eliminated if an acceptable oil temperature may beachieved without it, or the clutch solenoid may be eliminated ifdesired. Further, the above-described components may be locatedelsewhere on the housing.

Turning to FIGS. 4A and 4B, the pump assembly 50 is housed in theintermediate wall 33, which eliminates the need for a separate pumphousing typically used in the prior art. The intermediate wall 33 has anopening 110 that is in fluid communication with the inlet 46 and outlet48 ports. The inlet 46 and outlet 48 ports and the opening 110 are roughcast into the intermediate wall 33. At least one pumping member, or morespecifically, an inner 112 and outer 114 rotor, is dispose within theopening 110 for moving the oil from the inlet port 46 to the outlet port48.

Referring to FIG. 4B, the outer rotor 114 has an outer cylindricalsurface 116 adjacent a perimeter of the opening 110. The outer rotor 114has a plurality of radially inwardly extending teeth 120 and the innerrotor 112 is disposed within the outer rotor 114. The inner rotor 112has a plurality of radially outwardly extending teeth 122 that mesh withthe plurality of radially inwardly extending teeth 120 so that the inner112 and outer 114 rotors rotate together. A pump cover 126 is attachedto the intermediate wall 33 over the opening 110 and the inner 112 andouter 114 rotors. An inlet 128 and outlet 130 chamber is defined withinthe opening 110 by the pump cover 126 and space between the inlet 112and outlet 114 rotors.

The pump assembly 50 has a pump shaft 132 with first 134 and second 136ends. A bore 138 in intermediate wall 33 supports the pump shaft 132,and a bushing 140 is received within the bore 138. The first end 134 isreceived within a hole 141 in the inner rotor 112 and coupled theretousing an interlocking key 142 and notch 144. The second end 136 iscoupled to a pump gear 146 that is, in turn, coupled to a gear, such asthe reverse idler gear 31. As the gear 31 rotates, the inner 112 andouter 114 rotors are driven, which draws the oil from the inlet port 46into the inlet chamber 128 and then expels the oil into the outletchamber 130 and to the outlet port 48.

Referring to FIG. 5, the housing has an outer wall 148 with theintermediate wall 33 extending interiorly at an angle from it. The outerwall 148 has a hole 150 extending into the intermediate wall 33 whichintersects the inlet passageway 56. A filter 152 is disposed within thehole 150 between said sump 52 and inlet chamber 128 for filtering theoil as it moves from the sump 52 through the plurality of branches 58 tothe inlet passageway 56. A removable plug 154 is disposed within thehole 150 at an exterior surface 156 of the outer wall 148 for preventingthe oil from leaking from the housing 12 and providing access to thefilter 152. The filter 152 may or may not be connected directly to theplug 154.

As discussed above, the distribution system 44 carries oil totransmission components located throughout the housing 12. For example,the second passageway 72 lubricates the gears 30,31, in addition tolubricating the bearing portions 17. Referring to FIGS. 6 and 7, thesecond passageway 72 has at least one distribution port 160 proximate tothe gears 30,31 for delivering the oil to the gears 30,31. To this end,the second passageway 72 is located in the upper portion 70 of thehousing 12 above the gears 30,31. The distribution ports 160 are drilledthrough a surface 159 of the housing 12 and into the second passageway72.

With reference to FIGS. 7 and 8, the main box 14 and clutch housing 18each have a flange 162,163, respectively, that abut one another when themain box 14 and clutch housing 18 are fastened together. The oil travelsalong the second passageway 72 parallel to the shafts 22,24 and into theclutch housing 18 through an inlet opening 164 at the interface of theflanges 162,163. The oil then travels through the oil distributionsystem within the clutch housing 18 (shown in FIGS. 9 and 10) andreturns to the second passageway 72 in the main box 14 through outletopening 166. The flanges 162,163 are sealed together using a hightemperature liquid sealant.

FIGS. 9 and 10 show front portions of the clutch housing 18 that deliveroil to the bearings 60 that support the bearing portions 17 of theshafts 22,24. The distribution system 44 has a second passageway 72 thatcarries the oil to a third passageway 74 that intersects thecountershaft bores 60 to lubricate the bearing portion 17. Another thirdpassageway 74 carries oil from the second passageway 72 to the inputshaft bore 61, shown in FIG. 10. The oil is permitted to drain from thebore 60 to the sump 52 through return passageway 62.

In operation, the pump assembly 50 pumps oil from the collection system42 to the distribution system 44 to the transmission components, fromwhich it returns to the collection system 42. FIG. 11 shows the flow ofoil throughout the distribution system 40. The dashed lines indicate theoil flow path if some of the features of the present invention were notused. The pump assembly 50 draws the oil from the sump 52 through theplurality of branches 58 of the inlet passageway 56 and through thefilter 152. The pump assembly 50 draws the oil from the inlet port 46into the inlet chamber 128 and then expels the oil into the outletchamber 130 and to the outlet port 48.

The pump assembly 50 then moves the oil through the main feed passageway68 to the second 72 and third 74 passageways to deliver the oil to thegears 30,31 and bearing portions 17. The oil passes through the reliefvalves 92,98, solenoid 80 and oil cooler 96 as the oil travels throughthe second passageway 72.

The invention has been described in an illustrative manner, and it is tobe understood that the terminology that has been used is intended to bein the nature of words of description rather than of limitation.Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A transmission having an integral lubricationsystem for delivering lubricating fluid comprising: a housing having awall with an opening and inlet and outlet ports in fluid communicationwith said opening; a pump assembly having at least one pumping memberdisposed within said opening for moving the fluid from said inlet portto said outlet port; a pump cover attached to said wall over saidopening and said at least one pumping member; and an inlet and outletchamber defined within said opening by said pump cover said housing andsaid at least one pumping member, said inlet and outlet chambers beingin fluid communication with said inlet and outlet ports respectively,wherein said pumping member draws the fluid from said inlet port intosaid inlet chamber and then expels the fluid into said outlet chamberand to said outlet port.
 2. The transmission as set forth in claim 1wherein said pump assembly further includes a pump shaft, and whereinsaid wall further includes a bore that supports said pump shaft, saidpump shaft being coupled to said at least one pumping member, whereinsaid pump shaft rotates said at least one pumping member for moving thefluid from said inlet chamber to said outlet chamber.
 3. Thetransmission as set forth in claim 2 wherein said pump assembly furtherincludes a bushing disposed within said bore, wherein said bushingsupports said pump shaft.
 4. The transmission as set forth in claim 2wherein said at least one member includes inner and outer rotors, saidouter rotor having an outer cylindrical surface adjacent a perimeter ofsaid opening, said outer rotor having a plurality of radially inwardlyextending teeth, said inner rotor being disposed within said outerrotor, said inner rotor having a plurality of radially outwardlyextending teeth that mesh with said plurality of radially inwardlyextending teeth, wherein said inner and outer rotor rotate together. 5.The transmission as set forth in claim 4 wherein said pump shaft furtherincludes first and second ends, said first end being coupled to saidinner rotor, wherein said pump shaft rotatingly drives said inner rotor.6. The transmission as set forth in claim 5 further comprising aplurality of drive shafts supported by said housing, said plurality ofdrive shafts collectively having a plurality of drive gears thatcooperate to achieve a desired gear ratio, said pump assembly furtherincluding a pump gear coupled to said second end, said pump gear beingcoupled to one of said plurality of drive gears, wherein said one ofsaid plurality of drive gears rotatingly drives said pump gear.
 7. Thetransmission as set forth in claim 1 wherein said wall further includesfirst and second surfaces in spaced relation, the transmission furthercomprising: a sump defined by a portion of said housing for holding thefluid; and an inlet passageway interposed between said first and secondsurfaces, said inlet passageway interconnecting said inlet chamber andsaid sump to provide fluid communication therebetween, wherein said pumpassembly draws the fluid from said sump through said inlet passagewayinto said inlet chamber and then expels the fluid into said outletchamber.
 8. The transmission as set forth in claim 6 wherein saidhousing further includes an outer wall with said wall extendinginteriorly at an angle therefrom, said outer wall having a holeextending into said wall and intersecting said inlet passageway, thetransmission further comprising: a filter being disposed within saidhole for filtering the fluid moving through said inlet passageway. 9.The transmission as set forth in claim 1 wherein said wall furtherincludes first and second surfaces in spaced relation, the transmissionfurther comprising: a distribution system having a plurality of fluiddistribution ports for delivering the fluid to a plurality oftransmission components within said housing; and a main feed passagewayinterposed between said first and second surfaces, said main feedpassageway interconnecting said outlet chamber and said distributionsystem to provide fluid communication therebetween, wherein said pumpassembly draws the fluid into said inlet chamber and then expels thefluid into said outlet chamber and through said main feed passageway tosaid distribution system.
 10. The transmission as set forth in claim 1wherein said wall is an intermediate wall separating a main andauxiliary box of said housing.
 11. A transmission having an integrallubrication system for delivering lubricating fluid comprising: ahousing having a wall portion with first and second surfaces in spacedrelation; a sump defined by a portion of said housing for holding thefluid; a pump assembly having inlet and outlet chambers; an inletpassageway interposed between said first and second surfaces, said inletpassageway interconnecting said inlet chamber and said sump to providefluid communication therebetween, wherein aid pump assembly draws thefluid from said sump through aid inlet passageway into said inletchamber and then expels the fluid into said outlet chamber; filterinterposed between said sump and said inlet chamber; and said housingfurther includes an outer wall with said wall portion extendinginteriorly at an angle therefrom, said outer wall having a holeextending into said wall portion and intersecting said inlet passageway,said filter being disposed within said hole for filtering the fluidmoving through said inlet passageway.
 12. The transmission as set forthin claim 11 further comprising a removable plug disposed within saidhole adjacent to an exterior surface of said outer wall for preventingthe fluid from leaking from said housing and providing access to saidfilter.
 13. A transmission having an integral lubrication system fordelivering lubricating fluid comprising: a housing having a wall portionwith first and second surfaces in spaced relation; a sump defined by aportion of said housing for holding the fluid; a pump assembly havinginlet and outlet chambers; an inlet passageway interposed between saidfirst and second surfaces, said inlet passageway interconnecting saidinlet chamber and said sump to provide fluid communication therebetween,wherein said pump assembly draws the fluid from said sump through saidinlet passageway into aid inlet chamber and then expels the fluid intosaid outlet chamber; and said wall portion is an intermediate wallseparating a main and auxiliary box of said housing.
 14. A transmissionhaving an integral lubrication system for delivering lubricating fluidcomprising: a housing having a cast wall portion with first and secondsurfaces in spaced relation; a pump assembly having inlet and outletchambers; a distribution system having a plurality of fluid distributionports for delivering the fluid to a plurality of transmission componentswithin said housing; and a main feed passageway integrally formed withinsaid wall portion and interposed between said first and second surfaces,said main feed passageway extending from said outlet chamber to saiddistribution system to provide fluid communication therebetween, whereinsaid pump assembly draws the fluid into said inlet chamber and thenexpels the fluid into said outlet chamber and through said main feedpassageway to said distribution system.
 15. A transmission having anintegral lubrication system for delivering lubricating fluid comprising:a housing having a wall portion with first and second surfaces in speedrelation; a pump assembly having inlet and outlet chambers; adistribution system having a plurality of fluid distribution ports fordelivering the fluid to a plurality of transmission components withinsaid housing; a main feed passageway interposed between said first andsecond surfaces, said main feed passageway interconnecting said outletchamber and said distribution system to provide fluid communicationtherebetween, wherein said pump assembly draws the fluid into said inletchamber and then expels the fluid into said outlet chamber and throughsaid main feed passageway to said distribution system, and said wall isan intermediate wall separating a main and auxiliary box of saidhousing.